The U.S. Chamber of Commerce began airing an ad this week against Maine Senate frontrunner Angus King (I), knocking him for his financial management of the Pine Tree State during his eight-year tenure as governor.

The Chamber backs Republican Charlie Summers, who faces an uphill battle for the open seat of retiring Sen. Olympia Snowe (R). The effectiveness of the ad in knocking down King — widely liked in Maine — will probably go a long way to determining whether national Republicans make a push for the seat at all this fall.

http://www.youtube.com/watch?v=w4a3blFhcDo

Democrats and Republicans in Washington, D.C. expect King to caucus with Democrats, though he maintains he'll take the best deal he is given and caucus with the party that allows him the most independence.

"Angus King. Independent? His record tells a different tale," a male narrator says. "Angus King, he's the king of spending. While King was governor, state spending skyrocketed to $2.6 billion. The king of mismanagement: when King left office, he left Maine with a billion dollar budget shortfall."

A source familiar with the buy said the ad was backed by $288,000 on statewide broadcast and cable television from Tuesday through Aug. 6.

"We have been expecting these types of negative, ill formed attack ads," said King Communications Director Crystal Canney in a statement to Roll Call. "The U.S. Chamber's attack on Angus shows just how out of touch this organization is with business challenges in Maine. This is Washington politicos trying to tell people in Maine how to vote. Mainers and Maine businesses know Angus King has a strong record of support in the business community."

A spokeswoman for the Chamber declined to say how much the organization was spending on the ad.